Variable speed control trigger for electric switch



April 16, 1968 w. T. SORENS ON VARIABLE SPEED CONTROL TRIGGER FOR ELECTRIC SWITCH 2 Sheets-Sheet l INVENTOR lismy l'dapz/va'ow BY 9 ATTOR EY Filed July 25, 1967 A ril 16, 1968 w. T. SORENSON 3,378,662

VARIABLE SPEED CONTROL TRIGGER FOR ELECTRIC SWITCH I Filed July 25, 1967 2 Sheets-Sheet i:

:1 i 2 v 6; l I WVW //4/' A Tm lfl. 07 66 INV NTOR [6Z ATTORNEY United States Patent savanna VARIABLE srnnn contract. antenna non ntncrnic swrrcrr Wesley T. Sorenson, West Hartford, Conn, assignor to Carling Electric, Inn, West Hartford, Conn, a corporation of Connecticut Filed July 25, 1967, Ser. No. 655,888 12 Claims. (Cl. 200-157) ABSTRACT OF THE DISCLOSURE Plunger latch means for trigger control for operating variable speed switch for hand tool or the like.

BACKGROUND OF THE INVENTEON (1) Field of the inventi0n.-This invention relates to switches and, more particularly, to finger operated trigger controls for variable switches incorporated in the pistol grip portions of hand tools or the like.

(2) Description of the prior arz.Previous control devices for variable speed switches for operating hand tools or the like have been cumbersome and have not provided for even gradation of control from low speed to high speed, especially in view of the fact that variable control switches are only recently being incorporated into such hand tools. Also, previous trigger controls for tool switches have lacked conveniently manipulated means for locking the variable switch at a desired speed and easily operated means for releasing the locking means.

SUMMARY OF THE INVENTION The present invention comprises a variable electrical switch which may be incorporated into the pistol grip handle of a hand tool or the like wherein a finger operated element is retractable like a trigger to determine the amount of current delivered by said switch for producing different and varying speeds on the hand tool, with a thumb-operated element cooperating with said trigger element for securing the latter in a desired or set position to cause the tool to operate at constant speed. The thumb operated element is automatically releaseable upon further retraction of the trigger when no pressure is exerted on said thumb operated element.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a typical hand tool having a pistol grip trigger, with the switch therefor shown in dotted outline;

FIG. 2 is a perspective view of the trigger and switch element separated from the hand tool;

FIG. 3 is a top elevation of the device shown in FIG. 2;

FIG. 4 is a side view of the device shown in FIG. 2, some parts being broken away and some parts being shown in section;

FIG. 5 is a top view of the device shown in FIG. 4 with the trigger being partially retracted;

FIG. 6 is similar to FIG. 5 with the trigger shown retracted even further;

FIG. 7 is a greatly enlarged fragmentary top view of the device shown in FIGS. 2 to 6, while the trigger is partially retracted, some parts being shown in section and some parts being shown in elevation;

FIG. 8 is a greatly enlarged vertical section view of the device shown in FIG. 2, some parts being shown in elevation;

FIG. 9 is a perspective view of another embodiment of the invention;

FIG. 10 is a greatly enlarged fragmentary top view of a portion of the device shown in FIG. 9;

3,378,662 Patented Apr. 16, 1968 ice DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings in detail, there is shown in FIG. 1 a typical hand tool comprising a body 21, a chuck 22, and a drill bit 23 secured in said chuck. Contained within body 21 is an electric motor, not shown, for rotating said chuck and said drill bit. Body 21 has a pistol-grip handle 24 in which is located a switch 26 connected by means of lead lines 27 and 28 and cable 29 to a source of electric power, not shown. Switch 26 is connected to and controls the aforementioned electric motor in body 21.

An enlarged view of switch 26 is shown in FIG. 8 and comprises a pair of spaced apart movable contact fingers 31 and 32 which slidably cooperate with a pair of spaced apart, elongated contact elements in a manner well known in the art. Said contact elements may comprise a bus bar and a variable resistance element whereby the movement of contact fingers 31 and 32 thereover control the current transmitted through switch 26 to the motor for determining the speed at which said motor rotates. The remainder of the switch circuitry is located in a switch box suspended by suitable means below walls 34 and 36.

Contact fingers 31 and 32 are mounted on a block 33 which is movable longitudinally within a frame having a pair of side walls 34 and 36, a rear wall 37, and a top wall 33.

Top wall 38 has a pair of spaced apart longitudinal channels 39 into which spaced apart bosses 41 integrally formed on block 33 extend. The movement of block 33 is delimited by the respective ends of channels 39 which limit the longitudinal movement of bosses 41.

Blocks 33 has a recess at the rearward portion thereof forming an abutment shoulder 42 against which one end of spring 43 bears, the other end of said spring bearing against rear wall 37, said spring normally urging block 33 into the forward open circuit position as shown in FIGS. 2, 8, 9 and 12.

integrally formed on the forward portion of block 33 and extending through an opening in the forward portion of the switch frame is a trigger element 46 which also extends through an aligned opening in pistol-grip 24. When the hand of the operator holds pistol grip 24, the forefinger is able to engage trigger element 46 for retraction thereof against the action of spring 43. As trigger element 46 is retracted, contact fingers 31 and 32 move longitudinally over the circuit elements to vary the amount of current passed by switch 26 to the tool motor whereby the speed of the motor is controlled in accordance with the distance to which trigger element is retracted. When trigger element do is in the open circuit position shown in FIGS. 1, 2, 8, 9 and 12, at least one of contact fingers 31 and 32 is spaced apart from its corresponding circuit element whereby no electrical current is transmitted to the tool motor, thereby signifying that the switch is in the off position. As trigger element 46 is retracted, the switch circuit is initially closed and the variable resistor or other circuit control elements in the switch box will cause the motor to start at slow speed with increasing speed being determined by the proportional distance to which trigger element 46 is retracted. Accordingly, the operator can determine the speed of the tool motor and the drilling speed of bit 23 by maintaining continuous finger control of trigger 46 in a particular or desired retracted location.

When the hand tool is to be operated at a constant, predetermined speed for extended periods of time, finger con trol on trigger 46 may not only be inaccurate or inconstant, but it may also be fatiguing. Accordingly, means are provided for setting the trigger 46 in a desired static location, and locking said trigger in position in order to reiieve the operator of the necessity for maintaining constant finger pressure thereon. Locking means is disclosed in FIGS. 26 where the intermediate portion of the trigger element between block 33 and the forward portion of said trigger is recessed forming a floor 47 and a vertical side wall 48. Bounding the rear portion of said recess is a diagonal vertical abutment 49 at the top of which is a horizontal recess 51.

Secured in position on the horizontal surface of recess 51 is a plate 52 having rows of serrations or saw teeth 53 which are arrayed at an angle relative to the longitudinal motion traversed by trigger 46 and block 33. Plate 52 may be secured in recess 51 by any suitable means such as a pair of spaced apart rivets 54 or the like. In some embodiments, there may be substituted for rivets 54 a pair of screws which permit plate 52 to be removably attached to the device for replacement purposes due to wear or the like. Serrations 53 are preferably uniformly spaced apart along plate 52.

Mounted by suitable means on the outside surface of wall 34 of the switch frame is a guide tube 56 which slidably accommodates a lock button 57 movable longitudinally therein. Button 57 has a shaft 58 of reduced diameter which extends through an aperture 59 in wall 34, the inner end of said shaft terminating in a lock element 61 having an outwardly extending flange 62 or the like for engaging any one of serrations 53. Located within tube 56 is a coil spring 63 surrounding shaft 58, one end of said spring bearing against a shoulder 64 of button 57, the other end of which bears against wall 34 surrounding aperture 59. Spring 63 normally urges button 57 outwardly from tube 56 with flange 62 being urged against the inner surface of wall 34 to limit the outward movement of said button and causing the latter to be retained in position within tube 56. A suitable aperture is provided in the side wall of tool handle 24 for extending tube 56 therethrough to permit thumb operation of button 57.

When button 57 is depressed against the action of spring 63, flange 62 engages any of the serrations 53 of plate 52 depending upon the extent to which trigger 46 has been retracted against the action of spring 43. As shown in FIG. 3, for example, flange 62 is completely disengaged from the serrations or teeth of plate 52 when trigger 46 is in its forwardly extended position whereby the switch controlled thereby is in the open circuit condition. As shown in FIG. 5, trigger 46 has been retracted partially while button 57 has been depressed so that flange 62 interengages with one of the teeth or serrations 53 of plate 52 thereby locking trigger 46 in a desired position. In FIG. 6, trigger 46 is retracted still further and button 57 has been depressed even further to cause flange 62 to interengage with another tooth or serration 53 of plate 52.

It is evident from the foregoing that the operator can retract trigger 46 a sufiicient distance to bring about the desired current transmitting action of switch 26 at which time the operators thumb depresses button 57 to lock the trigger in the desired position. A very fast sequence of actions is possible by the forefinger retracting the trigger, and the thumb of the operator depressing the button to achieve the desired speed of the hand tool for drilling or the like.

It is evident that from time to time the speed of the hand tool can be changed rapidly by the operator retracting the trigger 46 even further and locking said trigger into the desired position by depressing button 57 still further.

By virtue of the diagonal array of serrations 53 relative to lock element 61, the hand tool can be switched rapidly to the off or open circuit condition by slightly retracting trigger 46 while button 57 is untouched whereby the engaged serration 53 moving rearwardly disengages from flange 62, as a result of which spring 63 causes said flange to move rapidly out of the path of the row of serrations 53 and to become disengaged therefrom, after which finger release of trigger 46 permits spring 43 to urge said trigger back into the off position, as shown in FIGS. 2 and 8, whereby switch 26 is returned automatically to the open circuit condition.

A further embodiment of the invention is disclosed in FIGS. 9 and 10 of the drawings wherein block 33 has a vertical recess 66 arrayed at an angle relative to the longitudinal path traversed by said block, said recess accommodating a plate 67 which may be secured therein by means of a layer 68 of adhesive or the like, or by other suitable bonding means. Plate 67, which may be made of a suitable tough metallic material or the like, has a plurality of spaced apart vertical notches 69, each of which are engageable by flange 62 of lock element 61 for retaining trigger 46 and block 33 in a desired location in the same manner as described in connection with the embodimet shown in FIGS. 27.

A still further embodiment of the invention is shown in FIG. 11 where the forward portion of block 33 has a vertical recess 71 which is bounded on each end by recesses 72 and 73 into which plate 74 may be removably inserted. Plate 74 also has a plurality of spaced apart vertical serations 76 which are engageable by flange 62 of lock element 61. When serrations 76 become worn or otherwise deteriorated and ineffectual, plate 74 may be removed and a fresh plate inserted. By this means, the life of the trigger switch device may be increased by the provision for the replacement of the single element that may become worn in use.

Another embodiment of the invention is disclosed in FIGS. 12 and 13 whereby the forward portion of block 33 is molded or otherwise formed in a row of serrations 77 which are arrayed at an angle relative to the longitudinal path traversed by said block. When serrations 77 are formed or molded integrally with block 33, the material of said block is chosen to have sufiicient hardness and toughness to withsand and endure a great number of interactions with flange 61 of lock element 62.

In all of the embodiments of the invention herein, the manipulation of the device is facilitated by arranging trigger 46 and lock button 57 relative to each other on handle 24 whereby trigger 46 is manipulated by the forefinger and button 57 is manipulated by the thumb of the operator of the hand tool. The retraction of trigger 46 and the depression of button 57 takes place virtually simultaneously to the extent desired by the operator when trigger 46 is to be locked in the desired location for providing a constant speed for the hand tool or the like. When trigger 46 is retracted to the desired location and button 57 is depressed to cause the interengagement between fiange 62 and one of the serrations 53, for example, trigger 46 and button 57 are maintained in their respective positions by said interlocking engagement and no further finger or thumb pressure is necessary to maintain the speed of the drill. When it is desired to stop the rotation of the motor drive of the hand tool, only trigger 46 need be retracted slightly by the forefinger whereby flange 62 will automatically become disengaged from seration 53 under the action of spring 63 which will also cause the complete retraction of flange 62 from the path of serrations 53 whereby both trigger 46 and block 33 will be urged by the action of spring 43 automatically into the open circuit condition as shown in FIGS. 2 and 3, for example.

,Under other conditions of use, the speed of the hand tool may be adjusted at any time by further manipulation of trigger 46 and button 57 for rapid setting of a dilferent desired speed. The provision of a plurality of closely spaced apart serrations 53, 69, 76 or 77 in the respective embodiments permits the setting of the tool speed at a great number of gradations between low speed and the high speed setting where trigger 46 is retracted to its fullest limit. Thus, the slight retraction of trigger 46 will cause the switch to close the circuit in which a variable resistor is contacted at its higher level to provide low speed operation of the tool, while the gradual retraction of trigger 45 causes one of the switch contacts to move over the variable resistor reducing the resistance factor of the latter until the high speed rotation is achieved at full retraction of trigger 46. In some embodiments, semiconductor devices may be incorporated into switch 2s which will perform a function similar to the variable resistor when trigger 46 is retracted.

Although the present invention has been described with reference to particular embodiments and examples, it will be apparent to those skilled in the art that variations and modifications can be substituted therefor without departing from the principles and true spirit of the invention. The Abstract given above is for the convenience of technical searchers and is not to be used for interpreting the scope of the invention or claims.

I claim:

1. A trigger switch for a hand tool or the like having a pistol grip handle, comprising a variable control electrical switch, a movable trigger on said handle connected to and operating said switch, biasing means in said handle normally urging said trig er into an open circuit position, the retraction of said trigger against said biasing means producing a gradation of control changes by said switch, a row of uniformly spaced apart serrations on said trigger, said row being disposed at an angle relative to the longitudinal movement of said trigger, a plunger mounted in said handle and movable laterally relative to the path of said trigger element, said plunger element being engageable with any selected one of said serrations to retain said trigger in a desired location.

2. A switch according to claim 1 wherein said trigger and said plunger are disposed relative to said pistol grip handle whereby said trigger is manipulated by the forefinger and the plunger is manipulated by the thumb of the operators hand.

3. A switch according to claim 1 and further comprising second biasing means normally urging said plunger out of engagement with said serrations.

4. A switch according to claim 3 wherein the interengaging portions of said serrations and said plunger are shaped in a manner that said plunger is automatically released from a particular serration upon the further retraction of said trigger against the action of said first mentioned biasing means.

5. A switch according to claim 1 wherein said row of serrations comprises a saw tooth plate mounted upon said trigger.

6. A switch according to claim 5 wherein said plate is removably attached to said trigger.

'7. A switch for a hand tool or the like having a pistol grip handle comprising a variable control electrical switch, first movable means connected to and operating said switch, biasing means in said handle normally urging said first means into an open circuit position, a plurality of spaced apart notches on said first means, said plurality of notches being disposed at an angle relative to the longitudinal movement of said first movable means, and second movable means on said handle movable into position to engage any selected one of said notches when said first means is retracted against said biasing means.

8. A switch according to claim 7 and further comprising a slot in said first means, a plate mounted and secured in said slot, said notches being located on said plate.

9. A switch according to claim 7 and further comprising second biasing means in said handle normally urging said second movable means out of engagement with said notches.

10. A switch according to claim 7 wherein said first and second movable means are located on said handle relative to each other whereby said first movable means is manipulated by the forefinger and said second movable means is manipulated by the thumb of the operator of the tool.

11. A switch according to claim 7 wherein said plurality of spaced apart notches are arrayed at an angle relative to the path traversed by said first movable means whereby the continued retraction of said first movable means against said biasing means requires an increasing movement by said second movable means to engage a selected one of said notches.

A switch according to claim 7 and further comprising second biasing means normally urging said second movable means out of the path of movement of said first movable means, the disengagement between said first movable means and said second movable means taking place when said first movable means is retracted slightly and said second movable means is automatically retracted from said notch by said second biasing means.

References Cited UNITED STATES PATENTS 2,994,726 9/1959 Ricketts 74-527 XR 3,309,484 3/1967 Frenzel 200-l57 3,356,814 12/1967 France 200-157 ROBERT K. SCHAE'FER, Primary Examiner.

H. BURKS, Assistant Examiner. 

